This invention relates to gears. More particularly, this invention relates to composite gears made from a rigid material such as metal as well as from a thermoplastic material.
Gears made from a rigid material such as metal or metal alloys are well known and are used in many applications. Such gears may withstand high torque load forces, but have a significant shortcoming in that they generate a great deal of noise when they mesh with other metal gears.
Gears made from a thermoplastic material are also known and have been used to reduce the noise generated by metal gears. However, thermoplastic gears have significant disadvantages, in that they cannot withstand high torque load forces without damaging their gear teeth, and are more susceptible to wear than metal gears.
To solve the respective problems of metal and thermoplastic gears, several attempts have been made to manufacture composite gears having some metal components and some thermoplastic components. U.S. Pat. No. 3,719,103 issued Mar. 6, 1973 to Streander discloses one such attempt in which a thermoplastic panel is sandwiched between two rigid steel plates, with the assembly being thereafter bolted together. One purpose of the gear in U.S. Pat. No. 3,719,103 is to increase the torque rating of the gear under normal load conditions as compared to gears having teeth which are made from a thermoplastic material alone. The increased torque rating is achieved by having the steel plates control the bending of the plastic material since the plastic is sandwiched between the two steel plates. The torque rating is increased so that higher loads may be borne under normal conditions.
Another object of the design in U.S. Pat. No. 3,719,103 is to reduce gear noise. Although some noise reduction is achieved in the patented design, significant noise will still be generated by the gear since the steel plates limit the bending of the plastic teeth.